What is a deadbolt? It is a lock whose solid bolt is projected into the door-frame strike by a key, thumbturn, or motor. Unlike a beveled spring latch, a dead bolt does not retract simply because pressure is applied to its end. That distinction matters before choosing a smart lock: identify the existing mechanical hardware and door preparation first, then compare the access, visibility, connectivity, and power features you want.
This guide explains the parts and types you may find on a US residential door, how current BHMA ratings work, and when a full-replacement smart deadbolt, an interior retrofit, or professional review is the sensible next step.
What is a deadbolt, exactly?
A deadbolt secures a closed door by extending a bolt into a strike mounted on the frame. Builders Hardware Manufacturers Association (BHMA) terminology distinguishes a dead bolt, which does not retract when pressure is applied to its end, from a latch bolt, which is usually beveled and can be pushed back as the door closes.
That mechanical distinction is more useful than the words “traditional” or “smart.” A smart lock can operate a deadbolt. A door can also have a smart latch, a mortise lock, or another architecture that is not interchangeable with a standard bored deadbolt.
| Feature | Dead bolt | Spring latch bolt |
|---|---|---|
| Typical shape | Solid, usually square-ended | Usually beveled |
| What moves it | Key, thumbturn, lever mechanism, or motor | Handle/knob mechanism and a spring |
| Retracts from pressure on the bolt end | No | Often yes |
| Primary everyday role | Securing the closed door | Holding the door closed and enabling normal passage |
If you searched “what is a deadbolt?” because you are shopping for a smart lock, the practical answer starts here: confirm which bolt and lock case are already in the door before comparing electronics.
Deadbolt parts and the measurements that matter
A good answer to “what is a deadbolt?” needs the vocabulary on both the door and frame. These terms help you read an installation guide, compare a new lock with your existing preparation, and describe a problem accurately.
| Part or measurement | What it is | Why it matters for smart-lock fit |
|---|---|---|
| Dead bolt | The solid bolt that projects from the door edge into the frame. | Its travel must be smooth and the strike must be aligned; a motor should not have to fight binding hardware. |
| Cylinder | The keyed component that accepts the key and operates the lock mechanism. | A full-replacement smart deadbolt may replace the exterior cylinder; an interior retrofit may keep it. |
| Thumbturn | The inside control that retracts or projects the bolt by hand. | Interior retrofit locks commonly replace or drive this side of the mechanism. |
| Case or bolt housing | The mechanism installed inside the door. | Its shape and dimensions distinguish common bored hardware from mortise or other systems. |
| Lock front or faceplate | The plate visible on the door edge around the bolt. | Its shape, screw pattern, and recess need to match the replacement latch or bolt assembly. |
| Strike | The frame-mounted plate that receives the bolt. | Misalignment can prevent complete locking even when the electronics work correctly. |
| Strike box | A box behind the strike that receives the projected bolt. | The opening needs enough depth and clearance for the bolt to extend fully. |
| Crossbore | The large round opening through the door face for bored lock hardware. | Its diameter affects whether exterior and interior assemblies seat correctly. |
| Edge bore | The smaller opening from the door edge to the crossbore. | It houses the bolt assembly and must suit the new hardware. |
| Backset | The distance from the door edge to the centerline of the cylinder or crossbore. | Replacement bolt assemblies are designed for particular backsets. Measure rather than assume. |
| Door thickness | The distance between the inside and outside door faces. | Screws, tailpieces, spindles, and mounting plates have supported thickness ranges. |
| Trim clearance | The open space around the lock, handle, molding, and any storm door. | A wide smart-lock body may fit the bores but still collide with nearby hardware. |
Measure the actual door. Do not use the outside trim diameter as a substitute for the crossbore, and do not assume an existing lock’s brand tells you the preparation underneath it. For a measurement walkthrough, see How to Install a Smart Lock.
What is a deadbolt cylinder?
The cylinder is the keyed component on the exterior side of a typical residential deadbolt. Turning the correct key rotates the mechanism that moves the bolt. Some full-replacement smart deadbolts replace this component, while an interior retrofit may leave it in place.
What is a deadbolt backset?
The backset is the distance from the door edge to the centerline of the cylinder or crossbore. Compare the measured distance with the exact replacement bolt assembly; appearance alone cannot confirm it.
Types of deadbolts
“Types of deadbolts” can refer to how the lock fits the door, how it is controlled from each side, or whether electronics operate it. Keep those three questions separate.
Bored deadbolt
A bored deadbolt—also called a tubular or cylindrical deadbolt in everyday shopping language—fits round openings bored through the door face and edge. This is the common architecture used by many residential replacement smart deadbolts, but hole size, backset, door thickness, handing, and clearance still need to match the exact model guide.
Mortise deadlock
A mortise deadlock is installed in a prepared cavity in the door edge. Its rectangular lock case and trim are fundamentally different from a standard round-bore deadbolt. A product made for a bored single-cylinder deadbolt should not be assumed to fit a mortise door.
Interconnected lock
An interconnected lock combines latch and deadbolt operation so one inside action can retract both. The hardware and egress behavior are part of the assembly. Replacing only one visible component without confirming the complete listed configuration may be inappropriate.
Smart deadbolt
A smart deadbolt uses electronics to authorize or actuate the deadbolt. Depending on the model, access might include a PIN, biometric method, app, credential, or mechanical key. “Smart” describes the control and connected features; it does not erase the underlying door-hardware requirements.
Single-cylinder vs. double-cylinder deadbolt
The word cylinder here describes keyed operation, not the round shape of the door bore.
| Type | Exterior side | Interior side | Important consideration |
|---|---|---|---|
| Single-cylinder deadbolt | Keyed cylinder | Thumbturn | Common residential arrangement and the starting point for many consumer smart-deadbolt and retrofit products. |
| Double-cylinder deadbolt | Keyed cylinder | Keyed cylinder | A key is required to unlock from inside. That can conflict with safe, quick egress and may be restricted by the requirements that apply to the opening. Do not convert one without checking locally. |
Hardware rules depend on the building, door, occupancy, and adopted code. A product page is not a substitute for your local authority, building manager, fire-door label, or qualified door-hardware professional.
What do deadbolt grades and ratings mean?
Deadbolt labels are easy to misread because more than one BHMA rating system appears in the residential market.
BHMA’s current residential deadbolt and deadlatch standard is ANSI/BHMA A156.40-2025. The standard covers performance areas including operation, durability, security and strength, and finish. Under BHMA’s residential Secure Home labeling program, certified products covered by A156.39 or A156.40 can receive separate Security, Durability, and Finish ratings: A (Best), B (Better), or C (Good).
You may also see Grade 1, Grade 2, or Grade 3 on hardware certified under other ANSI/BHMA standards. In that system, Grade 1 is the highest level. These numbers should not be casually translated into the residential A/B/C label, and one rating should not be presented as the product’s performance in every category.
When comparing deadbolt grades or ratings:
- Note the exact ANSI/BHMA standard and edition named.
- Check whether the label gives one grade or separate security, durability, and finish ratings.
- Match the certification to the exact product or model—not just the brand family.
- Verify the current listing in BHMA’s Certified Products Directory.
This article does not assign a grade or BHMA certification to a Lockin model. Use a current, model-specific listing before making that claim.
Is a smart lock still a deadbolt?
It can be. A deadbolt describes the locking hardware; a smart lock describes electronic access, actuation, or connectivity. Many smart locks are motorized deadbolts, while others operate latches, mortise cases, multipoint systems, or existing interior hardware.
This is why “smart lock vs. deadbolt” is not always an either-or choice. The useful comparison is:
- What mechanical architecture is in the door?
- Which components will the new product replace or operate?
- Does the exact model support the door preparation and required egress behavior?
- Which access and connected features are useful for the household?
For a broader explanation of electronic access and connectivity, read How Smart Locks Work.
Smart deadbolt vs. retrofit lock
The distinction between full replacement and retrofit is one of the quickest ways to narrow the field.
| Question | Full-replacement smart deadbolt | Interior retrofit smart lock |
|---|---|---|
| What changes? | Exterior trim/cylinder, interior assembly, and usually the bolt hardware | Usually the interior thumbturn or interior assembly; exterior hardware may remain |
| Exterior appearance | Changes | Often stays familiar |
| Key cylinder | May be replaced with the model’s supplied cylinder or backup method | Often retained, depending on the product |
| Fit checks | Door bores, backset, thickness, faceplate, handing, trim clearance, strike alignment | Existing deadbolt model/shape, tailpiece or adapter compatibility, interior clearance, smooth bolt movement |
| When it may suit | You want an integrated exterior keypad, biometric reader, camera, or complete new assembly | You want to preserve exterior trim and the existing keyed cylinder |
| Not a shortcut for | Mortise, multipoint, narrow-stile, fire-rated, or unusual doors without exact approval | A binding, damaged, misaligned, or unsupported deadbolt |
Neither design is automatically the right choice. Full replacement can add integrated exterior features; retrofit can preserve the outside appearance. The door and the exact product guide decide whether either approach fits.
Will a smart deadbolt fit your door?
Use this decision path before buying or removing hardware.
- Look for a stop condition. Pause if the door has a fire label, belongs to a shared or common egress path, is controlled by a landlord or building, or uses mortise, interconnected, multipoint, narrow-stile, French-door, storm-door, or other unusual hardware. Get model-specific and professional confirmation.
- Identify the architecture. A separate round deadbolt above a knob or lever is often a bored single-cylinder setup, but remove trim only when permitted and compare the hidden preparation with the installation guide.
- Measure the door. Record door thickness, crossbore diameter, edge-bore diameter, backset, faceplate shape, and the clearance around the lock. Check strike depth and alignment, too.
- Test the existing bolt. With the door open and then closed, it should travel freely. Correct door or strike alignment before asking a motor to move a binding bolt.
- Choose the replacement architecture. Decide whether you want a complete exterior-and-interior smart deadbolt or a supported interior retrofit.
- Check the exact current guide. Match every measurement and exclusion to the exact model and region. Family names and product photos are not sufficient evidence.
- Use a compatibility check before checkout. Start with the Lockin Smart Lock Selector, then confirm against the exact model’s current manual.
If any measurement falls outside the stated range—or if the door type is not explicitly supported—stop and ask the manufacturer or a qualified installer. Extra drilling can create a problem that a different product would have avoided.
Fire-rated and egress doors: stop before DIY changes
A fire door is an assembly: door, frame, glazing where present, and hardware work together. Changing the lock or drilling the door can affect that assembly’s listing and performance. UL guidance points installers to the door’s labels, the manufacturer’s instructions, the applicable edition of NFPA 80, and egress requirements.
Likewise, model building codes generally expect an egress door to be openable from the egress side without a key or special knowledge, subject to defined exceptions. The edition and amendments adopted where you live can differ.
Do not treat a double-cylinder lock, new bore, retrofit adapter, or smart-lock feature as automatically acceptable on a fire-rated, multifamily, rental, or shared-egress opening. Ask the property authority, local code official, fire-door professional, or qualified locksmith before changing it.
How this applies to Lockin Veno smart deadbolts
Lockin’s US selector groups Veno products as smart deadbolts and presents Veno Solar bundles as complete front-door replacement options. Models differ in access methods, video, solar assistance, smart-home features, and physical fit.
For the Veno products covered by current installation guides, plan for an exterior-and-interior assembly installation rather than assuming an interior-only retrofit adapter. That does not establish compatibility across the Veno family or across standard-looking doors. Current guides show model-specific differences in supported bore sizes, clearances, and exclusions, so the exact product page and current guide must control the decision.
Use this sequence:
- Identify the existing deadbolt architecture.
- Measure the door and surrounding clearance.
- Use the Smart Lock Selector.
- Compare the result with the exact model in the Lockin user-manual library.
- If the sources disagree or the opening is unusual, contact Lockin support or a qualified installer before altering the door.
You can browse the Lockin Veno smart deadbolt family after completing those fit checks.
Frequently asked questions
What is a deadbolt, and how is it different from a latch?
A deadbolt projects a solid bolt into the frame and does not retract when pressure is applied to the bolt end. A spring latch is usually beveled and can move inward as the door closes. A door may use both.
Can I replace a deadbolt with a smart lock?
Often, if the smart lock is designed for the existing architecture and the door’s bores, backset, thickness, handing, trim clearance, and strike alignment match its current guide. Mortise, multipoint, fire-rated, and shared-egress doors need additional review.
Is a smart lock the same as a deadbolt?
Not necessarily. “Smart lock” describes electronic access or operation; “deadbolt” describes mechanical hardware. A smart lock may be a complete deadbolt, an interior retrofit that operates an existing deadbolt, or another lock type.
What is a single-cylinder vs. double-cylinder deadbolt?
A single-cylinder deadbolt is keyed outside and normally uses a thumbturn inside. A double-cylinder deadbolt is keyed on both sides. Because the latter requires a key for inside egress, verify the rules and safety requirements for the specific opening before using or replacing one.
What deadbolt grade is best?
First identify the rating system. Many ANSI/BHMA standards use Grades 1, 2, and 3, with Grade 1 highest. The residential Secure Home program for A156.39 and A156.40 uses separate A, B, or C ratings for security, durability, and finish, with A highest. Compare the exact standard, category ratings, and certified model listing rather than the label alone.
Can I install a smart deadbolt on a fire-rated or shared-egress door?
Do not assume so. The door’s label, listed assembly, adopted building and fire requirements, property rules, and product instructions all matter. Obtain approval from the responsible authority and use a qualified professional before drilling or changing hardware.
Know the hardware before choosing the features
The most useful answer to “what is a deadbolt?” is not just a definition. It is a way to recognize the bolt, cylinder, strike, bores, and backset that determine whether a replacement can work safely and smoothly.
Identify the architecture, measure the preparation, check the exact current guide, and stop for professional review when the door is unusual or regulated. Then use the Smart Lock Selector to compare compatible Lockin options and the features that matter to your household.
Sources and standards
- BHMA Guide to Builders Hardware Terminology: Types of Locks
- ANSI/BHMA A156.40-2025: Residential Deadbolts and Deadlatches
- BHMA Product Grade Levels
- ANSI: BHMA Certified Secure Home Label
- ICC 2024 International Building Code, Chapter 10: Means of Egress
- ICC Code Adoption Resources
- UL: Fire-Rated Doors and Frames Guide
- UL: Fire Door Inspection and Field Evaluation